The processing of waste including municipal waste, medical waste, toxic and radioactive waste by means of plasma-torch based waste processing plants is well known. Referring to FIG. 1, a typical prior art plasma-based processing plant (1) comprises a processing chamber (10) typically in the form of a vertical shaft, in which typically solid, and also mixed (i.e., generally, solid plus liquid and/or semiliquid), waste (20) is introduced at the upper end thereof via a waste inlet means comprising an air lock arrangement (30). One or a plurality of plasma torches (40) at the lower end of the chamber (10) heats the column (35) of waste in the chamber (10), converting the waste into gases that are channeled off via outlet (50), and a liquid material (38) (typically molten metals and/or slag) which is periodically or continuously collected at the lower end of the chamber (10) via reservoir (60). Oxidising fluid, such as air, oxygen or steam (70) may be provided at the lower end of the chamber (10) to convert carbon, produced in the processing of organic waste, into useful gases such as CO and H2, for example. A similar arrangement for dealing with solid waste is described in U.S. Pat. No. 5,143,000, the contents of which are incorporated herein by reference thereto.
Waste cannot be fed into the chamber (10) until the column of waste (35) has descended sufficiently to accommodate the new waste therein. Thus, sufficient time needs to be given for the column to descend: if new waste is added too soon, it is possible that the air lock arrangement (30) may be damaged or may malfunction; if the time delay is too long, the throughput rate and efficiency of the apparatus is lowered.
In JP 10238744, a control system for operating an ash extraction means is described, including the detection of a burning layer at a predetermined height in the furnace. However, there is no disclosure or suggestion on how to automatically control the input of waste into a waste processing apparatus.
It is therefore an aim of the present invention to provide a control system for controlling the input of waste which overcomes the limitations of prior art systems.
It is another aim of the present invention to provide such a system incorporated as an integral part of a plasma-torch based type waste processing apparatus.
It is another aim of the present invention to provide such systems that are relatively simple and thus economic to produce as well as to maintain.
It is another aim of the present invention to provide a method for operating a plasma-based waste processing plant such as to optimize the feeding of waste thereto.